Systems and methods for uplink signaling using time-frequency resources

ABSTRACT

Methods, base stations and access terminals for uplink signaling are provided. Resource request channel characteristics such as location in time-frequency, sequence, time slot, are assigned to each access terminal to distinguish their resource requests from the resource requests of other access terminals. Access terminals make requests using a resource request on a resource request channel having the assigned characteristics. The base station can then determine which access terminal transmitted the resource request based on the resource request channel characteristics of the resource request channel upon which the resource request was received. The base station then transmits a response to the request which may for example be a new resource allocation, a default allocation or a renewal of a previous allocation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/677,438 filed Nov. 12, 2010, which is a National Phase Entry ofInternational PCT Application No. PCT/CA2008/001608 filed Sep. 11, 2008,which claims the benefit of U.S. Provisional Application No. 60/971,608filed Sep. 12, 2007, U.S. Provisional Application No. 61/046,596 filedApr. 21, 2008, U.S. Provisional Application No. 61/050,303 filed May 5,2008, and U.S. Provisional Application No. 61/094,159 filed Sep. 4,2008, all of which are incorporated by reference herein in theirentireties for all purposes.

FIELD OF THE INVENTION

The invention relates to wireless communication, and more specificallyto methods and systems for requesting uplink signaling.

BACKGROUND OF THE INVENTION

Uplink (UL) signaling generally refers to transmissions from an accessterminal to a base station in a wireless system. Uplink signaling canrequire significant resources, and may include several componentmessages such as ACK (acknowledgement)/NAK (negative acknowledgement),CQI (channel quality indicator) feedback in respect of the channel, MIMO(multiple input, multiple output) configuration, pilot channel, andresource requests to name a few specific examples.

Uplink signaling is used for many different applications. Some servicesmay be less delay sensitive, for example FTP (file transfer protocol),HTTP (hypertext transfer protocol), and other services may be more delaysensitive. Examples of some delay sensitive services include VoIP (Voiceover internet protocol), video telephony, near-real time video, andgaming.

In addition, some services have other challenges such as a limitedbandwidth and power for signaling, frequent transmissions of delaysensitive traffic, a requirement for signaling per packet or and pertransmission, large number of mobile stations, variable packet sizes, arequirement for adaptive MCS (modulation and coding schemes) forvariable size packets, and a requirement for adaptive resourcescheduling.

Some existing solutions have incurred a lot of overhead or delay, andhave not been able to accommodate a large number of mobile stationsefficiently.

In Draft IEEE 802.16m System Description Document, IEEE802.16m-08/003r1, dated Apr. 15, 2008, it is stated that:

-   -   This [802.16m] standard amends the IEFF 802.16 WirelessMAN-OFDMA        specification to provide an advanced air interface for operation        in licensed bands. It meets the cellular layer requirements of        IMT-Advanced next generation mobile networks. This amendment        provides continuing support for legacy WirelessMAN-OFDMA        equipment.    -   The standard will address the following purpose:        -   i. The purpose of this standard is to provide performance            improvements necessary to support future advanced services            and applications, such as those described by the ITU in            Report ITU-R M.2072.

FIGS. 7-13 of the present application correspond to FIGS. 1-7 of IEEE802.16m-08/003r1. The description of these figures in IEEE802.16m-08/003r1 is incorporated herein by reference.

SUMMARY

Various approaches to sending a resource request are provided. Theseinclude:

-   -   the persistent assignment of channel resources for transmission        of the resource requests—this can be an entirely new allocation,        or can be an allocation of some or all of a set of existing        signaling opportunities for resource request transmission        purposes;    -   the superposition of resource requests over other traffic in        which case interference cancellation techniques may be used at        the base station to remove interference due to the superimposed        resource request message;    -   the superposition of resource requests over other signaling in        which case again interference cancellation techniques may be        used at the base station to remove interference due to the        superimposed resource request message.

A broad aspect provides a method, for execution by a base station orother access network component or components, the method comprising:

-   -   assigning a respective set of at least one resource request        channel characteristics to each of a plurality of access        terminals for each access terminal to use to request uplink        transmission resources, each set of at least one resource        request channel characteristics being distinct from each other        set of at least one resource request channel characteristics;    -   receiving a resource request on a resource request channel;    -   determining which access terminal transmitted the resource        request based on at least one resource request channel        characteristic of the resource request channel upon which the        resource request was received;    -   transmitting a response to the request.

A second broad aspect provides a method in an access terminal, themethod comprising:

-   -   receiving an assignment of a set of at least one resource        request channel characteristic, the set of at least one resource        request channel characteristic being distinct from each other        set of at least one resource request channel characteristics        assigned to another access terminal;    -   transmitting a resource request on a resource request channel        having the set of at least one resource request channel        characteristic, the set of at least one resource request channel        characteristic identifying the access terminal as a source of        the request;    -   receiving a response to the request.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present application will now be described, by way ofexample only, with reference to the accompanying drawing figures,wherein:

FIG. 1 is a block diagram of a cellular communication system;

FIG. 2 is a block diagram of an example base station that might be usedto implement some embodiments of the present application;

FIG. 3 is a block diagram of an example wireless terminal that might beused to implement some embodiments of the present application;

FIG. 4 is a block diagram of an example relay station that might be usedto implement some embodiments of the present application;

FIG. 5 is a block diagram of a logical breakdown of an example OFDMtransmitter architecture that might be used to implement someembodiments of the present application;

FIG. 6 is a block diagram of a logical breakdown of an example OFDMreceiver architecture that might be used to implement some embodimentsof the present application;

FIG. 7 is FIG. 1 of IEEE 802.16m-08/003r1, an example of overall networkarchitecture;

FIG. 8 is FIG. 2 of IEEE 802.16m-08/003r1, a relay station in overallnetwork architecture;

FIG. 9 is FIG. 3 of IEEE 802.16m-08/003r1, a system reference model;

FIG. 10 is FIG. 4 of IEEE 802.16m-08/003r1, the IEEE 802.16m protocolstructure;

FIG. 11 is FIG. 5 of IEEE 802.16m-08/003r1, the IEEE 802.16m MS/BS dataplane processing flow;

FIG. 12 is FIG. 6 of IEEE 802.16m-08/003r1, the IEEE 802.16m MS/BScontrol plane processing flow;

FIG. 13 is FIG. 7 of IEEE 802.16m-08/003r1, generic protocolarchitecture to support multicarrier system;

FIG. 14 is an example of a distributed resource for resource request;

FIG. 15 is an example, of a localized resource for resource request;

FIG. 16 is an example of an access terminal access and resourceallocation flow;

FIG. 17 is a graphical depiction of an initial access channel;

FIG. 18 is a graphical depiction of an access channel used for initialaccess and resource request;

FIG. 19 is another graphical depiction of an access channel used forinitial access and resource request;

FIG. 20 is another graphical depiction of an access channel used forinitial access and resource request; and

FIG. 21 is a graphical depiction of a tile that is divided into twosections for the purpose of uplink signaling.

DETAILED DESCRIPTION

Various methods are provided to signal a request for a resourceassignment for an UL (uplink) transmission by an access terminal. Anaccess terminal is any device that is used to access a wireless network.Access terminals may be mobile stations or fixed wireless terminal forexample. Throughout this description, such a request is referred to as a“resource request”. It is to be understood that this refers generally toa request to be granted an opportunity to make an uplink transmission ortransmissions. It is noted that the signaling or other traffic may use anumber of transmission methods including but not limited to:

-   -   Orthogonal frequency division multiplexing (OFDM) based schemes;    -   OFDM with subcarrier-hopping sequences; and    -   Code division separation CDMA based or combinations thereof.

In some implementations the physical resource used comprises OFDMsymbols. In some embodiments, these symbols are organized into framesthat in turn are composed of subframes, each sub-frame containing aplurality of symbols. In some embodiments, a plurality of frames composea superframe.

In some embodiments the unit of resource allocation for uplinktransmission is a RB (resource block). The physical structure of aresource depends on the system implementation. In some embodiments, onthe uplink each resource block is defined as a physically contiguoustile in an OFDM time-frequency space. In other embodiments, on theuplink each resource block is defined as a distributed set of resourcetiles.

Some embodiments involve the assignment of a respective set of at leastone resource request channel characteristics to each of a plurality ofaccess terminals for each access terminal to use to request uplinktransmission resources, each set of at least one resource requestchannel characteristics being distinct from each other set of at leastone resource request channel characteristics. Access terminals can thenmake a resource request using the assigned set of at least one resourcerequest channel characteristics, and this is used by the base station todetermine who sent the request. Examples of characteristics include anassigned unique spreading sequence; an assigned unique location intime-frequency, an assigned time slot. Combinations may also be used,for example a spreading sequence and location in time-frequency in whichcase the spreading sequence alone need not be unique, and the locationin time-frequency need not be unique, but the combination of thespreading sequence and the location is distinct from the combinationassigned to other access terminals.

(A) Reserved Segment of Time-Frequency or Time-Frequency-Space for ULSignaling

In a first approach, a reserved resource within an uplink transmissionresource having time and frequency dimensions is employed and dedicatedsolely to the purpose of uplink signaling. In some embodiments, thespace dimension may be employed for MIMO (multiple input, multipleoutput) applications. The size, nature, frequency of such reservedresource is implementation specific, and depends upon the nature of theuplink transmission resource.

An OFDM (orthogonal frequency division multiplexing) transmissionresource is an example of a transmission resource having time andfrequency dimensions. The frequency dimension consists of a set ofsub-carriers, and the time dimension consists of OFDM symbol durations.

In some embodiments, the reserved resource is a contiguous block withinthe time-frequency OFDM transmission resource.

In some embodiments, code division separation is used by the accessterminals to distinguish the transmissions of each access terminaland/or to distinguish a type of signaling being performed. For example,in some embodiments each access terminal is assigned a sequence from aset of sequences. Each access terminal transmits its resource requestusing its assigned sequence. The base station that receives the requestcan determine which access terminal transmitted the request bydetermining which sequence was used. In some embodiments, the sequencesare orthogonal.

Superposition of Resource Request on Traffic and/or Other Signaling

In some embodiments, some or all of the transmission resource used fortransmission of the resource requests is the same as that used fortraffic and/or other signaling, typically by a different accessterminal, within a time-frequency transmission resource space. This isreferred to superposition or overlaying of transmissions. In someembodiments resource requests can be overlaid over the entire signalingbandwidth. This approach may provide the advantage of not designating aspecific resource set for signaling. In some embodiments, code divisionseparation UL signaling can be used with this method. This type ofsignaling may be useful for, but not limited to, resource requestsignaling for delay sensitive applications.

In some such embodiments, after a resource request is detected, it canbe removed from the traffic channel over which it was superimposedthrough interference cancellation (IC).

(B) Superposition of Resource Request on Traffic and/or Other Signalingon Persistent Resource

In some embodiments, superposition of resource requests over trafficand/or other signaling is performed using a persistent resource. Apersistent resource is a transmission resource that is known to theaccess terminal and the base station that occurs recurringly and as suchdoes not need to be signaled in a detailed manner each time it is to beused. In some embodiments, the persistent resource is a periodicresource assigned to a unique access terminal. In other embodiments,several access terminals may share a persistent resource assignment inwhich case some collisions may occur. In some embodiments, code divisionseparation UL signaling can be used with this method. This type ofsignaling is useful for, but not limited to, resource request signalingfor delay sensitive applications.

In some such embodiments, after a resource request message is detected,it can be removed from the traffic channel over which it wassuperimposed through interference cancellation (IC).

(C) Superposition of Resource Request on Traffic and/or Other Signalingon Specific Resource or Set of Resources

In some embodiments, the superposition of resource requests on trafficand/or other signaling on a specific resource or set of resources isemployed. In some embodiments, the transmission of the uplink signalingon a given set of resources indicates the access terminal is requestingassignment on those resources. In some embodiments, an access terminalmay be identified by a unique spreading sequence, or set of sequences.In some embodiments, the UL signaling may be sent only over the “first”resource block of a desired assignment.

(D) Unique Persistent Resource Assigned to Each Access Terminal or to aSet of Access Terminals

In some embodiments, a persistent recurring resource for UL signaling isassigned to each access terminal. This makes detection of the resourcerequest signal relatively simple at the base station, as the basestation only need look for a resource request from the particular accessterminal on that access terminal's assigned resource. With thisapproach, there is no contention for the capacity to transmit a resourcerequest. The resource may be dedicated to resource request transmission,or may overlaid over traffic and/or signaling as described in methods Band C above.

In another embodiment, a number of different persistent recurringresources are assigned, and each of the different persistent recurringresource is assigned to one or more access terminals. In this case,there is contention for the capacity to transmit a resource request, butonly with other access terminals assigned the same persistent recurringresource. In some embodiments, different spreading codes are assigned toaccess terminals that are assigned the same persistent recurringresource. The resource may be dedicated to resource requesttransmission, or may overlaid over traffic and/or signaling as describedin methods B and C above.

In some embodiments, this approach is used in conjunction withoverlaying the signaling over traffic or other signaling. In a specificexample, the following approach is followed:

-   -   If an access terminal has packet to transmit, it will transmit        signaling using its assigned resource.    -   The base station will receive signaling. In response, an        assignment is made to the access terminal for uplink        transmission.    -   The BS may have assigned some or all of the resource assigned to        the access terminal for resource request signaling to another        access terminal in this slot. In some embodiments, for the        purpose of receiving the transmission of the other access        terminal, interference cancellation can be used to remove the        effects of the resource request signaling.    -   If the access terminal does not have a packet, it does not        transmit anything using its assigned resource. The resource is        left blank, and no assignment message is sent for that access        terminal.

Resource Request Content

Resource request content refers to what is conveyed by the resourcerequest. In some embodiments, this may be spread using one or morespreading sequences as described below.

In some embodiments, the resource request content is only a flag orindicator as opposed to a message that might include additional fields,so that the detection of the flag or indicator is a request for apredefined response from the base station. In some embodiments, thepredefined response to the detection of an UL indicator for an accessterminal is to assign resources for at one least HARQ (hybrid automaticrepeat request) transmission on the UL. As a specific example, theindicator may be a request for a fixed size assignment for VoIPtransmission.

In some embodiments, the resource request contains multiple fieldsincluding one or more of desired resource, CQI, MIMO method, etc.

In some embodiments, one or more bits are used to indicate: signalingresource for transmission of default parameters and size. For example 1to 3 bits might be transmitted, each spread using a spreading sequence.Using a specific set of more than one bit can improve detection byreducing false alarm probability. Detection is all that is needed as thesequence(s) are assigned to a specific access terminal or user, and thetransmission of this signaling is just to indicate that a packet isready for transmission at the access terminal. This signaling can beused like a “page” of some kind.

In some embodiments, fields such as PF (packet format)/resource size,CQI with sub-band index (sub-band spans several resources), CRC might beincluded in the resource request. In some embodiments, the fieldsincluded may be variable. For example, a CQI might be included forrequests in respect of initial transmissions, and then omitted forrequests for retransmissions.

In some embodiments initial resource may be different from subsequentresource requests. An initial resource request is one at that initiatesa service, or re-configures such as service. Subsequent requests can beuse to renew or maintain such as service.

In some embodiments, the UL resource request for an access terminal is4-10 bits in size. In some embodiments, the initial resource requestmessage contains limited fields. In a specific example, the requestincludes QoS and 1^(st) transmission spectral efficiency/or accessterminal buffer size including CRC. This can be reliably signaledthrough the use of diversity.

In some embodiments, the resource request is combined with othermessages to include other feedback, for example ACK/NAK feedback.

In some embodiments with persistent resource for UL signaling, trafficintended for the access terminal may also use the persistent resourcefor one or more HARQ transmission.

In some embodiments, several different uplink messages may bemultiplexed using a combination of the described methods and procedures.

In some embodiments, the resource request is an indication to the basestation that an access terminal requires UL resource(s) on whichtransmit.

In some embodiments, the resource request is an indication to the basestation that an access terminal requires the use of a UL resource(s)previously assigned to it.

The methods for uplink signaling have been described in the context oftransmitting resource requests. In other embodiments, one or more ofthese approaches is used by the access terminal to indicate to the basestation one or more parameters associated with an UL assignment or ULassignment scheduling.

More generally still, the embodiments described thus far have focused onproviding mechanisms for transmitting resource requests, although asindicated above, these mechanisms may also be used for other types ofuplink signaling.

In some embodiments access terminals perform signaling for one or moreof initial access to a system, resource request, to trigger renewal ofnegotiated service, and to propose an allocation re-configuration.

Details on the designs for each type signaling. In addition, an accessand resource allocation flow is described. Several signaling structuresand channels are described herein. One or more of these structures andchannels can be used together, or separately.

In some embodiments, an assignment message transmitted on the downlinkto the access terminal containing a resource allocation is also used asa confirmation that the resource request was received. Upon receipt, theaccess terminal begins UL transmission using the assigned resource, beit a newly assigned resource, or a persistent resource.

In some embodiments, the resource request is spread by a spreadingsequence. The spreading may be in time, frequency or bothtime/frequency. For example, the signaling may be spread over a set ofsubcarriers in one or several OFDM symbols. FIG. 14 shows an example ofcode division spreading for OFDM transmissions using a distributedresource within an available time-frequency OFDM resource. FIG. 15 showsan example of code division spreading for OFDM transmissions using acontiguous resource. In some embodiment, orthogonal spreading sequencesmay be used. In other embodiments, non-orthogonal spreading sequencesare used.

For example, a spreading length 128 might be employed, but other lengthsare possible.

In some embodiments, direct sequence CDMA may also be used.

In some embodiments, each access terminal is assigned a respective setof sequences to use.

In some other embodiments, all access terminals are assigned the sameset of sequences to facilitate detection at the base station.

In some embodiments, orthogonal sequences such as Zadoff-Chu or Walshsequences may be used.

In some embodiments, the sequence length is less than the capacity of aRB. If N RB's are assigned for each resource request channel, thesequence may be repeated over all RB's.

In some other embodiments, the sequence may be spread over all N RB's.

In some embodiments, signaling can be configured per transmission, perpacket, or per multiple packets or with defined combinations of thesegranularities. In some cases, relatively frequent signaling may reducesome packet delay. Per transmission signaling allow for frequentscheduling of re-transmissions. The reliability of signaling may bereduced if it is per transmission.

In some embodiments, the resources for UL signaling are shared by a setor all access terminals. in some embodiments, the resources for ULsignaling may be a large portion or all of the resources.

Selecting Between Transmission Resources

In some embodiments, the access terminal has the capability of selectingbetween several different persistent resources to transmit its resourcerequest. In some such embodiments, the access terminal selects thepersistent resource that has been idle the longest. This may have theeffect of reducing the collisions.

Access Terminal Access and UL Resource Allocation Flow Example—FIG. 16

Referring now to FIG. 16, shown is an example of an access terminalaccess and UL resource allocation flow. Shown is functionality forinitial access, generally indicated at 200, and functionality forresource allocation, generally indicated at 202. An overview of FIG. 16will be provided first, followed by detailed example implementations forseveral of the steps. Note that various embodiments may include anarbitrary subset of the steps/functionality shown in FIG. 16.

Initial access 200 begins with an access request in block 204 using arandom access channel. The access terminal signals on a contention basedresource using a randomly selected sequence from a set of sequences. Thebase station responds with an access grant in block 206. This caninclude for example an initial DL/UL access grant, MAC (medium accesscontrol) ID, etc. Grant ID is based on access signaling. The “accessgrant” from the BS is a message sent to the access terminal. In someembodiments, the message is sent with a Grant ID to target the accessterminal. As the access terminal may not been identified except to senda “randomly selected sequence”, the grant ID in this case can be basedin some way the “randomly selected sequence”, or access signaling.

In some embodiments, in block 208, using the initial UL assignment, theaccess terminal signals access details such as MAC ID, if alreadyassigned. At that point, the access terminal has successfully accessedthe system. In some embodiments as part of block 208, a re-configurationheader is embedded in the first uplink packet transmission, i.e., thepacket transmitted using the initial UL assignment, to specify detailsof a resource request, such as further specifications about theassignment, MIMO mode, backlog of buffer at the access terminal, etc.

Resource allocation 202 begins with a UL resource request at block 210.The access terminal signals an initial resource request that may forexample be to start a service. This may for example be performed using ascheduled or non-scheduled resource. The base station responds at block212 with a UL resource assignment. This may include a DL access grant,etc., and UL assignment for service specification. As indicated below,the access terminal may specify or re-configure the service within theallocation using a MAC header. Next, the access terminal begins UL datatransmission 214 using the UL resource thus assigned. In someembodiments, the access terminal then has the option of signaling are-configuration of the service. This may, for example, be signaled aspart of a MAC header of a packet sent using the existing allocation. Insome embodiments, the MAC header may be sent alone. In some embodiments,the resource allocation protocol allows the access terminal to signal arenewal of the service. This may, for example, be signaled as part of aMAC header of a packet sent using the existing allocation or a MACheader sent alone. In response, as part of block 212, further ULresource assignment may be transmitted to the access terminal. At block216, the access terminal transmits a UL service renewal. This is sentusing an access terminal/service specific ID. In response, as part ofblock 212, a further UL resource assignment may be transmitted to theaccess terminal. The response is a UL assignment consistent withconfiguration negotiated before (persistent resource, MIMO mode, size ofresource, etc.)]

Details of example implementation of several of the blocks shown in FIG.16 will now be described.

Access Request 204

As indicated above, the process begins when the access terminal attemptsto access the system. At this point in common cases, the access terminalhas already synchronized with a serving sector. A random access (RA)channel is used for an access terminal to initially access the system.Access to the system may provide the access terminal with an Accessterminal ID (such as a MAC ID), and allow the access terminal to receiveresource allocations (UL and/or DL) from the base station. The physicalstructure of the random access channel is implementation specific. Threespecific options, each of which will be described in further detailbelow, include:

-   -   Option 1: random access channel uses a designated resource;    -   Option 2: random access channel is overlaid on UL control        resource (superposition with UL control);    -   Option 3: random access channel is overlaid on wideband UL        resources (superposition with traffic, etc).        A common aspect of these options is that the access terminal        randomly selects an access channel signaling ID (identifier).        The nature of the available signaling IDs is implementation        specific. It may for example be a specific spreading sequence,        time-frequency location, time slot, interlace, etc. Specific        examples are provided below. The set of signaling ID options are        known to base stations and access terminals. An index may be        associated with each signaling ID option that is also known to        the base stations and access terminals.

In some embodiments, in response to a random access channel signal, thebase station transmits an assignment message that assigns one or more ofthe following:

-   -   an access terminal ID to the access terminal;    -   an initial UL resource for the access terminal to provide        further information such as access terminal equipment        capabilities, etc.;    -   a possible DL resource assignment requesting information from        the access terminal, and additional details (group assignment,        base station procedures, etc).

In addition, in some embodiments, the assignment message sent to theaccess terminal from the base station identifies the base station basedon the randomly selected signaling ID option selected by the accessterminal for random access. For example, in some cases the controlchannels are normally generally scrambled in some manner by a sequenceassociated with the access terminal ID. In some embodiments, in responseto a random access signaling (for example during initial access to thesystem), the base station will send a control message scrambled by asequence associated with the randomly selected signaling ID instead ofthe access terminal ID. In some embodiments, the randomly selectedsignaling ID is an ID specifying one or more parameters such as sequenceindex, sequence location, etc.

In some embodiments, a subset of the defined signaling ID's are reservedfor access terminals that have already been assigned access terminalID's. An example of such an access terminal is an access terminal thatis in hand-off, and is attempting to access a new serving sector. Inthis case, an access terminal access terminal randomly selects from afirst subset of a defined set of random access signaling IDs if it doesnot yet have an assigned access terminal ID, and a different subset ofthe defined set of random access signaling IDs if it does have an accessterminal ID.

Option 1—Dedicated Resource for UL Access Channel

The first above-referenced option for the UL random access channelinvolves use of a designated resource allocated for these accessrequests. A contention based channel for multiple access terminals torequest access is employed. The access request is spread and/or repeatedacross a resource allocated exclusively for initial access. In someembodiments, the resource is allocated for initial access or resourcerequests. Specific examples are provided below. In the event theresource allocated for the random access channel includes multipledifferent transmission location possibilities (for example multiplelocations in an OFDM time-frequency resource), the access terminalrandomly selects a location of the multiple different locationpossibilities.

In some embodiments, the access terminal randomly selects a sequencefrom a set of L sequences known to both the access terminal and the basestation.

In some embodiments, the sequence length is selected so as to span NRB's, where N>1.

In some other embodiments, the sequence length is chosen to confine afull sequence to be transmittable using a single RB. For embodiments inwhich a RB is a contiguous block, and in which the sequences areorthogonal to begin with, by confining spreading sequence transmissionto one RB, the spreading sequences maintain substantial orthogonality asa contiguous RB is typically virtually frequency flat.

In some embodiments, the sequences are repeated in each of a pluralityRB to gain diversity.

If many resources are assigned for the random access, the resources maybe divided into M time-frequency blocks for random access. In such anembodiment, the number of distinct codes+resource combinations persubframe is L×M. In some embodiments, the value of M can be dynamicallyspecified by the BS.

In some embodiments, a subframe within a frame or superframe (orotherwise specified set of F frames) for an access request is alsorandomly selected. In this case, the number of distinctcodes+resource+subframes per superframe is L×M×F.

In some embodiments, the L sequences are an orthogonal set of spreadingsequences.

In some embodiments, the L sequences are divided into two groups so asto allow sequence selection to make two types of indications:

-   -   1) system access request from an access terminal without        previously assigned access terminal ID;    -   2) system access request from an access terminal with previously        assigned access terminal ID.

When an access grant is transmitted in response to such a request, insome embodiments the DL control segment access grant is scrambled by asequence associated with the randomly selected access ID (e.g.,sequence/resource block ID).

An example of this approach is depicted in FIG. 17. Here, the availableresource is an OFDM time-frequency resource. Frequency is on thevertical axis, and time is on the horizontal axis. Each box in FIG. 17,also referred to as a “tile”, represents a contiguous set ofsub-carriers over a number of OFDM symbols forming a subframe. Note thatthe entire vertical axis is not shown; it is assumed that there is a setof N×M tiles in the vertical direction available for use as accesschannels, where M is the number of initial access locations persub-frame, and N is the number of tiles per initial access location. Inthe illustrated example, N=3, but this is implementation specific. Foreach of the M initial access locations within a sub-frame, a set of N=3tiles is assigned. Thus, for example, the three tiles 240 labeled “A”are assigned as one initial access location. Other initial accesslocations can be assigned for a set of F subframes making up a frame orsuperframe. F=4 in the illustrated example, but this is implementationspecific. Within a given access location, any of L different sequencescan be used. Thus, the total number of distinct codes+resource+subframespermutations that can be accommodated is given by L×M×F.

In some embodiments, the above-described approach is used for resourcerequests in addition to, or instead of for requesting access.

Option 2—UL Access Channel Overlaid with UL Control

With this option, the UL random access channel is again a contentionbased channel for multiple access terminals to request access. Therandom access requests are overlaid with resources allocated to ULcontrol. The request is spread/repeated across the resources used forUplink Control (CQI, etc.). The access terminal randomly selects thelocation if multiple possibilities are available.

In some embodiments, the access terminal randomly selects a sequencefrom a set of L sequences known to both the access terminal and the basestation.

In some embodiments, the sequence length is selected to which spans NRB's, where N>1.

In some other embodiments, the sequence length is chosen to confine afull sequence to be transmittable using a single RB. For embodiments inwhich a RB is a contiguous block, and in which the sequences areorthogonal to begin with, by confining spreading sequence transmissionto one RB, the spreading sequences maintain substantial orthogonality asa contiguous RB is typically virtually frequency flat.

In some embodiments, the sequences are repeated in each of a pluralityRB to gain diversity.

If many resources are assigned for uplink control, the resources may bedivided into M time-frequency blocks for random access. In such anembodiment, the number of distinct codes+resource combinations persubframe is L×M. In some embodiments, the value of M can be dynamicallyspecified by the BS.

In some embodiments, the subframe within the frame or superframe (orotherwise specified set of F frames) for an access request is alsorandomly selected. In this case, the number of distinctcodes+resource+superframes per subframe is L×M×F.

In some embodiments, the L sequences are an orthogonal set of spreadingsequences.

In some embodiments, the L sequences are divided into two types ofindications:

-   -   1) system access request from an access terminal without        previously assigned access terminal ID;    -   2) system access request from an access terminal with previously        assigned access terminal ID.

When an access grant is transmitted in response to such a request, theDL control segment access grant is scrambled by a sequence associatedwith the sequence used to generate the resource request and/or thelocation of the frequency request in terms of time-frequency locationand/or subframe so as to associate the response with the request.

The base station can attempt interference cancellation to remove the RAchannel from UL control.

In some embodiments, the above-describe approach is used for resourcerequests in addition to, or instead of for requesting access.

Option 3—UL Random Access Channel Overlaid Over Wideband UL Resource

With this option, UL random access channel is a contention based channelfor multiple access terminals to request access that employs a resourcethat is overlaid over the UL resources available for control andtraffic. The request is spread/repeated across a portion of the ULchannel, possible the entire bandwidth. The access terminal randomlyselects the location if multiple possibilities are available.

For this embodiment, random access operation for all access terminals isassigned one length L sequence, and location if multiple possibilitiesare available.

In some embodiments, the total available resources blocks, N_(T), may bedivided into M time-frequency blocks for random access each defining arespective location for an access sequence. The access sequence spans(through spreading and repetition) N_(T)/M=N RBs (e.g., N=3).

In this case, the number of possible distinct requests per subframe isM. The access terminal randomly selects one of the M possibilities.

In some embodiments, the subframe within a frame or superframe for therequest is also randomly selected by the access terminal.

In some embodiments, the sequences for random access are an orthogonalset of spreading sequences.

In some embodiments, two sequences are defined for two types ofindications:

-   -   1) system access request from an access terminal without        previously assigned access terminal ID;    -   2) system access request from an access terminal with previously        assigned access terminal ID.

When an access grant is transmitted in response to such a request, theDL control segment access grant is scrambled by a sequence associatedwith the location and sequence used so as to uniquely associate theresponse with the resource request, and effectively identify the accessterminal.

In some embodiments, the base station can attempt interferencecancellation to remove the RA channel from UL control.

In some embodiments, as an alternative to, or in addition to usinginterference cancellation, the base station may try decoding UL controland traffic transmissions with two possibilities: with and without theassumption that a random access request was sent.

In some embodiments, the above-described approach is used for resourcerequests in addition to, or instead of for requesting access.

Access Grant/Initial Assignment 206

If the access terminal has sent a signaling option that indicates itdoes not have an access terminal ID, then in response to the initialaccess request, the base station sends a control message containing anaccess terminal ID scrambled by a sequence associated with the randomaccess signal ID.

If the access terminal has sent a signaling option indicating it doeshave an access terminal ID, then the base station sends a controlmessage scrambled by a sequence associated with the random accesssignaling ID, and the response need not contain an access terminal ID.In this case, the access terminal indicates its access terminal ID inthe next UL transmission containing details such as access terminalequipment capabilities, etc.

Resource Request 214

Once an access terminal has accessed the system, when the accessterminal has information to transmit to the base station, the accessterminal needs to request resources on the UL to do so. The specifics ofthis are implementation specific. Several specific options each of whichwill be described in detail below include:

-   -   Option 1: use UL control resource;    -   Option 2: use random access channel with scrambling sequence;    -   Option 3: overlay request on wideband resources; optionally CRC        protected.        Option 1—UL Resource requests Use UL Control Resource

With this option, resource requests are made using dedicated resourceswithin resources allocated to control. Note this is distinct fromoverlaying the request over the control resource; rather, part of thecontrol resource is used for resource requests rather than other typesof control signaling. In some embodiments, the control resource isformed of a set of UL control tiles, a control tile being a contiguousblock of time-frequency space allocated for control signaling. In someembodiments, the presence of a resource request is specified by an ULcontrol message type.

In some embodiments, the dedicated UL control resources are specifiedpersistently for each access terminal. In some embodiments, the amountof resource allocated to an access terminal in this manner is differentfor different frames according to a pre-determined pattern. The sizesare known at the access terminal and base station and do not need to besignaled after configuration.

In some embodiments, the resource request may occupy a field nominallyprovisioned for some other message, for example CQI, ACK/NAK, precoderindex, etc. The presence of a request may be specified by the UL controlmessage type. In order to transmit the resource request, the accessterminal sets the UL control message type to a message configurationthat includes space for a resource assignment. Therefore, the size ofthe message does not necessarily need to be changed from the specifiedsize for that subframe. With this approach, the presence of the resourcerequest field is dynamic, but does not affect the pre-determined size ofthe access terminal's UL control resource.

In some embodiments, the resource request is encoded with other ULcontrol data for the access terminal so that resource request can bereliably received.

In some embodiments, the resource request is a single “on/off”indication. In this case, details of the assignment can be given in are-configuration message, or known from previous or defaultconfigurations.

In some embodiments, the resource request is a message. Some details ofthe assignment such as delay constraints, QoS, packet backlog, resourcesize, etc. can be indicated in the resource request. Further details ofassignment can be given in a re-configuration message, or known fromprevious or default configurations.

In some embodiments, both the on/off indication and the more detailedresource request message approaches are possible using two differenttypes of resource request message, with a control message type beingspecified dynamically.

In some embodiments, the UL control resource can be specified by asecondary broadcast channel. In some embodiments, UL resources can beallocated across distributed RB's blocks.

In some embodiments, a resource request is 4-10 bits indicating QoS and1^(st) transmission spectral efficiency/or access terminal buffer size.

Option 2—Resource Requests Use Random Access Channel with ScramblingSequence

Details of an example access channel design in which access channelsequences/locations are used for define a set of random access signalingIDs have been described above. With this embodiment, a similar approachis used for the purpose of resource requests. In some embodiments, theapproach is used both for initial access and resource requests. The ULresource request uses a contention based channel for multiple accessterminals to request UL transmission resources. After system access, anaccess terminal is assigned one of a set of random access signaling IDs(i.e., channel sequences/location). Resource requests are thentransmitted using this sequence/channel configuration.

In some embodiments, access terminals may also be assigned specificsubframes for resource request opportunities. The presence of signalingin the assigned resource is a unique identifier for an access terminal'sresource request.

In some embodiments, a set of signaling ID's are reserved for resourcerequests that cannot be used for initial access. The assignedsequence/location is a unique identifier for an access terminal'sresource request. Each access terminal is assigned one signaling ID toidentify signaling as resource request signaling of a particular accessterminal.

In some embodiments, each access terminal is assigned one signaling IDfrom a full set of signaling ID's. In some embodiments, the sequence isscrambled by a resource request specific scrambling sequence to identifythe request as a resource request as opposed to a request for initialaccess. In this case, the assigned sequence/location/scrambling is aunique identifier for a particular access terminal's resource request.

In some embodiments, an access terminal may be assigned multiplesignaling ID's for different configured services. For example, an accessterminal might be assigned one for VoIP resource requests, one for httptraffic resource requests, etc.

In some embodiments in which option 2 is available, if a given accessterminal has another mechanism for resource request (e.g., option 1described above), and opportunities for requests are frequent the mobiledevice may not be necessarily assigned signaling for transmittingresource requests in using option 2.

An example of the approach introduced above in which a set of accesschannel locations is divided between initial access and resource requestutilization will be described with reference to FIG. 18. Shown is a setof access channel locations within a single subframe. The layout issimilar to that described previously with reference to FIG. 17. There isa set of M access channels having associated access channel IDs “ACHSignal ID 0”, . . . , “ACH Signal ID M−1”. Note that the example depictsonly a single resource block per access channel, but alternativelymultiple resource blocks per access channel maybe defined as in theexample of FIG. 17. The access channel locations are divided into twotypes. The top n_(ACH) locations, generally indicated at 250, areassigned for initial access use. The bottom M−n_(ACH) locations,generally indicated at 252, are assigned for resource request use. Insome embodiments, the division of the available locations betweeninitial access and resource requests, as defined by the parametern_(ACH), is signaled, for example as part of superframe information. Inthis manner, it can be made configurable based on traffic conditions. Asin other embodiments described herein, multiple signaling resources canbe assigned to the same access terminal for multiple service requests.

An example of the approach introduced above in which a set of accesschannel locations is not divided between initial access and resourcerequest utilization, and in which scrambling is used to separate accessrequests from resource requests will be described with reference to FIG.19. Shown is a set of access channel locations within a single subframe.The layout is similar to that described previously with reference toFIG. 17. There is a set of M access channel channels having associatedaccess channel IDs “ACH Signal ID 0”, . . . , “ACH Signal ID M−1”. Notethat the example depicts only a single resource block per accesschannel, but alternatively multiple resource blocks per access channelmaybe defined as in the example of FIG. 17.

For the embodiment of FIG. 19, an initial access request specificsequence is employed for access requests. Such a request can be madeusing any of the M available locations in a subframe that is randomlyselected by an access terminal that needs to make an access request. Forexample, the access channel location 260 having “ACH Signal ID 1” mightbe randomly selected by an access terminal to make an initial accessrequest. In some embodiments, multiple specific sequences are used tospecify whether the request is handoff or initial access.

For the embodiment of FIG. 19, a resource request specific sequence isemployed for access requests. Each access terminal is assigned aspecific location for the purpose of making resource requests. In theillustrated example, access channel location 262 having ACH Signal IDn_(MS1) has been assigned to a first access terminal, and access channellocation 264 having ACH Signal ID n_(MS2) has been assigned to a secondaccess terminal. A given access channel location will only contain aresource request if the specific access terminal assigned to thelocation has transmitted a resource request.

In yet another example in which the random access channel is used forboth initial access and resource requests, the available differentsignaling IDs are each assigned to one of a plurality of request types.A specific example of such a set of request types includes:

-   -   Initial access;    -   Initial access with already assigned access terminal ID (i.e.,        handoff);    -   Resource request type 1: basic;    -   Resource request type 2: renewal of service;    -   Resource request type 3: predefined configuration.

An example of this is depicted in FIG. 20 in which:

-   -   Access channel locations identified as ACH Signal ID 0, . . . ,        ACH Signal ID n₁−1 are assigned to request type 1, as generally        indicated at 270;    -   Access channel locations identified as ACH Signal ID n₁, . . . ,        ACH Signal ID n₂−1 are assigned to request type 2, as generally        indicated at 272;    -   and so on.

In some embodiments, the division of the signaling IDs between thevarious indications may be configurable by the base station, for examplebased on traffic.

As in other embodiments described herein, multiple signaling resourcescan be assigned to the same access terminal for multiple servicerequests.

Option 3—UL Resource Request Overlaid Request on all UL Resources

With this embodiment, the UL resource request uses resources specifiedpersistently. These may include one or multiple RB's. Multiple RB's maybe distributed to provide diversity. The UL resource request is overlaidwith other traffic/control on some or all of the same resources astraffic/control.

In some embodiments in which Option 3 is available, if a given accessterminal access terminal has another mechanism for resource request (forexample option 1 described above), and opportunities for requests arefrequent enough, it may not necessarily be assigned signaling fortransmitting resource requests using Option 3.

In some such embodiments, interference cancellation is used at the BS toremove the effects of the resource request from other traffic/controltransmissions. The resource requests of different access terminals areseparated by the location of RBs and/or and subframe, and/or assignedsequences.

UL Data Transmission 210

In some embodiments, as part of a transmission using an existingallocation, an access terminal can embed a header on a packettransmission which can provide details/parameters on configuration, orreconfiguration on an assignment.

After an access terminal has been assigned a UL resource, the assignmentcan be further configured through additional message(s) embedded in datapacket. In some embodiments, the parameters for the first transmissionare specified in a resource request, set to default values based oncapability negotiation, set to a previous configuration based onrenewal, or set in some other manner.

The access terminal can change the assignment parameters by includingadditional re-configuration message(s) encoded with data packets, totake effect at the start of the next packet transmission. This has thebenefit of taking advantage of HARQ for this control message, assumingof course that HARQ is in place for the packet transmission.

In a specific example, a field is appended to a packet prior toencoding, and a field in the header of the packet is used to indicatethe presence and/or type of service re-configuration message. Afterdecoding at the base station, the header is examined to determine if anadditional re-configuration message has been added to the packet withre-configuration information.

The following is a specific example of header operation:

-   -   2-bit header field to indicate presence, and type of service        re-configuration message as follows:        -   ‘00’ no change to configuration, no re-configuration            message;        -   ‘01’ no change to configuration, no re-configuration            message, extend service for another packet;        -   ‘10’ re-configuration message attached: Type 1        -   ‘11’ re-configuration message attached: Type 2

The re-configuration message can contain changes to the existingassignment, or future assignments including for example:

-   -   Mobile power header room;    -   Update of capabilities;    -   Request for different MIMO mode;    -   Request for different MCS;    -   Indication of mobile data backlog size;    -   Indication to continue assigning UL resources until data backlog        is emptied;    -   Resource size specification;    -   Delay requirement, QoS, etc.;    -   Request of an additional service/resource;    -   Other transmission parameters.

In some embodiments, the header (and possible message) is added to onlya first packet transmission, for example the first packet in a series ofpacket transmissions (talk spurt, file download, etc.)

In some embodiments, the header (and possible message) is added to thefirst packet transmission, and every N.sup.th packet afterwards, where Ncan be one or larger.

ACK/NAK of packet transmission from the base station can be used toprovide the access terminal with an indication that the re-configurationmessage was correctly received.

Renewal of Service 216

A renewal for service is signaling transmitted by the access terminal tothe base station to indicate a renewal of a configured service. Becauseit is simply a renewal, the message size can be very small; for example,details such as a size of a requested allocation do not need to beincluded. The specifics of the channel for transmitting this areimplementation specific. Several specific options, each of which will bedescribed in detail below, include:

-   -   Option 1: use UL control resource    -   Option 2: use random access channel with scrambling sequences

Option 1—Renewal Uses UL Control Resource

In this embodiment, after an access terminal has received a ULassignment for a given type of service, the assignment can be renewedthrough a single renewal message. An existing assignment may haveexpired, or been stopped (e.g., Silence period in VoIP) or may have onlyexisted for one packet and its HARQ transmissions. In some embodimentsthe renewal message is simply an ON/OFF toggle to renew service withprevious or existing parameters. With this embodiment, the renewalmessage is sent using part of a persistently assigned UL controlresource space. The message may have a message type to indicate thatservice renewal is being signaled. In some embodiments, an accessterminal can be assigned multiple messages to allow toggling of multipleservices. In some embodiments, a downlink feedback field is replacedwith the renewal message.

In some embodiments, the parameters of the renewal process (i.e.,location in the control resource allocated for renewal) for a firsttransmission are set to a default. In some embodiments, re-configurationin a first transmission can be used to provide parameter changes.

This approach is useful, for example, for an access terminal to switch aVoIP service from inactive to active state.

Option 2—Renewal Uses Use Random Access Channel with ScramblingSequences

After an access terminal has received a UL assignment for a given typeof service, the service can be renewed through a single message. Themessage may be a simple an ON/OFF toggle to renewal service withprevious or existing parameters. In this embodiment, the message is sentusing a resource request using a random access resource, such asdescribed above for example, to renew service to the last set ofconfiguration parameters.

In some embodiments, an access terminal can be assigned multiplemessages to allow toggling of multiple services.

In some embodiments, the parameters of the renewal process for a firsttransmission are set to default values.

System with Two Mechanisms for Resource Requests and Renewal Requests

Details have been provided above of the use of a contention basedchannel (random access channel) approach for resource requests and theuse of a contention based channel (random access channel approach forrenewal requests. In addition, details have been provided above of theuse of control resources for resource requests, and the use of controlresources for renewal requests. In another embodiment, two differentmechanisms are implemented one of which is contention based, and theother of which uses UL control resources, and a given access terminalchooses between the two mechanisms.

First Mechanism: Contention Based Mechanism for Resource Requests andRenewal Requests

An indication is sent to the base station specifying that the accessterminal requires a resource assignment. The base station responds withan allocation of a preconfigured resource assignment, a renewal of anexisting service, or a default allocation. The further configuration ofthe resource request can be specified in a MAC message embedded in thetransmissions.

The indication occurs using the access channel signaling ID's, but isscrambled by a resource renewal or resource request specific scramblingsequence. In some embodiments, such an indication can also oralternatively be sent on the access terminal specific UL resources.

Second Mechanism: UL Control Resource for Resource/Renewal RequestMessage

A message is sent to the base station specifying that the accessterminal requires a resource assignment along with some parameters ofthe assignment such as delay constraints, QoS, packet backlog, resourcesize, etc., to name a few examples of what might be included. Thismessage is sent on the access terminal specific UL control resources.

With this embodiment, the access terminal can choose the form(indication vs. message) and location (random access channel vs. ULcontrol resource) of the transmission. For example, in some cases, theaccess terminal's assigned UL control resources may occur infrequently,in which case the access terminal might select the random access channelmechanism.

In some embodiments, the sequences are scrambled by sector ID andaccess/request type. For resource request channel, the request typespecifies a request for a pre-configured service or assignment. Multiplerequest types can distinguish between requests for different services,such as VoIP, data traffic, etc.

Example of a Physical Structure for Uplink Signaling

A detailed example of another physical structure for uplink signalingwill now be described. This can be used for some of the ULsignaling/resource requests described previously and/or for other uplinksignaling purposes such as ACK/NAK, CQI feedback, resources requests,etc. to name a few specific examples.

In some embodiments, the uplink signaling method described here can beused as a mechanism by which the access terminal signals the basestation (or other serving transmitter) and uniquely identifies itself tothe base station in the process. In this manner the base station knowswhich specific access terminal sent the UL signaling, and may takeappropriate action (for example, a predefined response).

A resource is assigned for uplink signaling, for example resourcerequests that includes a single tile or multiple distributed tiles,where a tile is physically contiguous set of subcarriers and OFDMsymbols within a resource set. A specific example is depicted in FIG. 21in which each tile is 6 subcarriers by 6 symbols, and three such tiles280, 282, 284 are available for uplink signaling within a subframe orframe.

In some embodiments each tile is divided into different sections. In theillustrated example, each tile 280, 282, 284 is divided into twosections—a first section occurring over the first three OFDM symbolsgenerally indicated at 290 and a second section occurring over thesecond three OFDM symbols generally indicated at 292. It should beapparent that this approach can be generalized to the division of tilesinto a plurality of sections.

In some embodiments, an access terminal is assigned a respectivesequence to be used for UL signaling in each section of the tile. Forexample, in tile 280, the access terminal uses a sequence from a firstsequence set of L₁ sequences in section 294, and uses a sequence from asecond sequence set of L₂ sequences in section 296. The two sequencesets may be the same or different. The number of permutations of pairsof sequences including a sequence from the first set and a sequence fromthe second set is L₁×L₂. Each access terminal is uniquely identified bythe pair of sequences used. In some cases, more than one access terminalmay be assigned the same sequence in one or more of the sequence sets,but not in all sequence sets.

In some embodiments, the mapping of sequences to the tile is repeated toother distributed tiles to exploit frequency diversity. For example, theaccess terminal that employs tile 280 to transmit its sequences may alsouse tiles 282 and 284.

In some embodiments, there may be multiple sets of tiles for signaling.The particular set of tiles assigned to the access terminal, incombination with the sequences assigned, uniquely identify the accessterminal.

In some embodiments, the spreading sequences used may be orthogonalsequences.

In some embodiments, the manner by which the sequences are mapped can bechanged from tile to tile. This is depicted in the example illustratedin FIG. 20 in which the area for the first sequence set occurs duringthe first three OFDM symbols 290 for tiles 280, 284, and occurs duringthe second three OFDM symbols 292 for tile 282, and in which the areafor the second sequence set occurs during the second three OFDM symbols292 for tiles 280, 284, and occurs during the first three OFDM symbols290 for tile 282.

While the example has focused on the use of this uplink signaling methodspecifically for resource requests, it can be used for other purposessuch as periodic ranging, ranging, CQI feedback, or other notificationfrom the access terminal.

Some embodiments have included the multiplexing of initial accesschannels and resource request in the same resource, and/or using thesame sequences. In some embodiments, the resource request channel isconfigured according to embodiments described, but independently of theinitial access channel which may or may not be present, or otherchannels described herein. For example, in some embodiments the resourcerequest channel can have structure according to the embodimentdescribed, whereas the random access channel uses an unrelatedstructure. In addition, in some embodiments it may not be appropriate toshare the same OFDM symbol structure for resource request and initialaccess channels. In these case, the resource request channel, or accesschannels, can be implemented according to the embodiments herein butapplied to each channel independently.

Wireless System Overview

Referring to the drawings, FIG. 1 shows a base station controller (BSC)10 which controls wireless communications within multiple cells 12,which cells are served by corresponding base stations (BS) 14. In someconfigurations, each cell is further divided into multiple sectors 13 orzones (not shown). In general, each base station 14 facilitatescommunications using OFDM with mobile and/or wireless terminals 16 (moregenerally access terminals), which are within the cell 12 associatedwith the corresponding base station 14. The movement of the mobilestations 16 in relation to the base stations 14 results in significantfluctuation in channel conditions. As illustrated, the base stations 14and mobile stations 16 may include multiple antennas to provide spatialdiversity for communications. In some configurations, relay stations 15may assist in communications between base stations 14 and wirelessterminals 16. Wireless terminals 16 can be handed off 18 from any cell12, sector 13, zone (not shown), base station 14 or relay 15 to an othercell 12, sector 13, zone (not shown), base station 14 or relay 15. Insome configurations, base stations 14 communicate with each and withanother network (such as a core network or the internet, both not shown)over a backhaul network 11. In some configurations, a base stationcontroller 10 is not needed.

With reference to FIG. 2, an example of a base station 14 isillustrated. The base station 14 generally includes a control system 20,a baseband processor 22, transmit circuitry 24, receive circuitry 26,multiple antennas 28, and a network interface 30. The receive circuitry26 receives radio frequency signals bearing information from one or moreremote transmitters provided by mobile stations 16 (illustrated in FIG.3) and relay stations 15 (illustrated in FIG. 4). A low noise amplifierand a filter (not shown) may cooperate to amplify and remove broadbandinterference from the signal for processing. Down conversion anddigitization circuitry (not shown) will then down convert the filtered,received signal to an intermediate or baseband frequency signal, whichis then digitized into one or more digital streams.

The baseband processor 22 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 22 is generallyimplemented in one or more digital signal processors (DSPs) orapplication-specific integrated circuits (ASICs). The receivedinformation is then sent across a wireless network via the networkinterface 30 or transmitted to another mobile station 16 serviced by thebase station 14, either directly or with the assistance of a relay 15.

On the transmit side, the baseband processor 22 receives digitized data,which may represent voice, data, or control information, from thenetwork interface 30 under the control of control system 20, and encodesthe data for transmission. The encoded data is output to the transmitcircuitry 24, where it is modulated by one or more carrier signalshaving a desired transmit frequency or frequencies. A power amplifier(not shown) will amplify the modulated carrier signals to a levelappropriate for transmission, and deliver the modulated carrier signalsto the antennas 28 through a matching network (not shown). Modulationand processing details are described in greater detail below.

With reference to FIG. 3, an example of a mobile station 16 isillustrated. Similar to the base station 14, the mobile station 16 willinclude a control system 32, a baseband processor 34, transmit circuitry36, receive circuitry 38, multiple antennas 40, and mobile stationinterface circuitry 42. The receive circuitry 38 receives radiofrequency signals bearing information from one or more base stations 14and relays 15. A low noise amplifier and a filter (not shown) maycooperate to amplify and remove broadband interference from the signalfor processing. Down conversion and digitization circuitry (not shown)will then down convert the filtered, received signal to an intermediateor baseband frequency signal, which is then digitized into one or moredigital streams.

The baseband processor 34 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 34 is generallyimplemented in one or more digital signal processors (DSPs) andapplication specific integrated circuits (ASICs).

For transmission, the baseband processor 34 receives digitized data,which may represent voice, video, data, or control information, from thecontrol system 32, which it encodes for transmission. The encoded datais output to the transmit circuitry 36, where it is used by a modulatorto modulate one or more carrier signals that is at a desired transmitfrequency or frequencies. A power amplifier (not shown) will amplify themodulated carrier signals to a level appropriate for transmission, anddeliver the modulated carrier signal to the antennas 40 through amatching network (not shown). Various modulation and processingtechniques available to those skilled in the art are used for signaltransmission between the mobile station and the base station, eitherdirectly or via the relay station.

In OFDM modulation, the transmission band is divided into multiple,orthogonal carrier waves. Each carrier wave is modulated according tothe digital data to be transmitted. Because OFDM divides thetransmission band into multiple carriers, the bandwidth per carrierdecreases and the modulation time per carrier increases. Since themultiple carriers are transmitted in parallel, the transmission rate forthe digital data, or symbols, on any given carrier is lower than when asingle carrier is used.

OFDM modulation utilizes the performance of an Inverse Fast FourierTransform (IFFT) on the information to be transmitted. For demodulation,the performance of a Fast Fourier Transform (FFT) on the received signalrecovers the transmitted information. In practice, the IFFT and FFT areprovided by digital signal processing carrying out an Inverse DiscreteFourier Transform (IDFT) and Discrete Fourier Transform (DFT),respectively. Accordingly, the characterizing feature of OFDM modulationis that orthogonal carrier waves are generated for multiple hands withina transmission channel. The modulated signals are digital signals havinga relatively low transmission rate and capable of staying within theirrespective bands. The individual carrier waves are not modulateddirectly by the digital signals. Instead, all carrier waves aremodulated at once by IFFT processing.

In operation, in some embodiments, OFDM is used for at least downlinktransmission from the base stations 14 to the mobile stations 16. Eachbase station 14 is equipped with “n” transmit antennas 28 (n≧1), andeach mobile station 16 is equipped with “m” receive antennas 40 (m≧1).Notably, the respective antennas can be used for reception andtransmission using appropriate duplexers or switches and are so labelledonly for clarity.

When relay stations 15 are used, OFDM is preferably used for downlinktransmission from the base stations 14 to the relays 15 and from relaystations 15 to the mobile stations 16.

With reference to FIG. 4, an example of a relay station 15 isillustrated. Similar to the base station 14, and the mobile station 16,the relay station 15 will include a control system 132, a basebandprocessor 134, transmit circuitry 136, receive circuitry 138, multipleantennas 130, and relay circuitry 142. The relay circuitry 142 enablesthe relay 14 to assist in communications between a base station 16 andmobile stations 16. The receive circuitry 138 receives radio frequencysignals bearing information from one or more base stations 14 and mobilestations 16. A low noise amplifier and a filter (not shown) maycooperate to amplify and remove broadband interference from the signalfor processing. Down conversion and digitization circuitry (not shown)will then down convert the filtered, received signal to an intermediateor baseband frequency signal, which is then digitized into one or moredigital streams.

The baseband processor 134 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 134 is generallyimplemented in one or more digital signal processors (DSPs) andapplication specific integrated circuits (ASICs).

For transmission, the baseband processor 134 receives digitized data,which may represent voice, video, data, or control information, from thecontrol system 132, which it encodes for transmission. The encoded datais output to the transmit circuitry 136, where it is used by a modulatorto modulate one or more carrier signals that is at a desired transmitfrequency or frequencies. A power amplifier (not shown) will amplify themodulated carrier signals to a level appropriate for transmission, anddeliver the modulated carrier signal to the antennas 130 through amatching network (not shown). Various modulation and processingtechniques available to those skilled in the art are used for signaltransmission between the mobile station and the base station, eitherdirectly or indirectly via a relay station, as described above.

With reference to FIG. 5, a logical OFDM transmission architecture willbe described. Initially, the base station controller 10 will send datato be transmitted to various mobile stations 16 to the base station 14,either directly or with the assistance of a relay station 15. The basestation 14 may use the channel quality indicators (CQIs) associated withthe mobile stations to schedule the data for transmission as well asselect appropriate coding and modulation for transmitting the scheduleddata. The CQIs may be directly from the mobile stations 16 or determinedat the base station 14 based on information provided by the mobilestations 16. In either case, the CQI for each mobile station 16 is afunction of the degree to which the channel amplitude (or response)varies across the OFDM frequency band.

Scheduled data 44, which is a stream of bits, is scrambled in a mannerreducing the peak-to-average power ratio associated with the data usingdata scrambling logic 46. A cyclic redundancy check (CRC) for thescrambled data is determined and appended to the scrambled data usingCRC adding logic 48. Next, channel coding is performed using channelencoder logic 50 to effectively add redundancy to the data to facilitaterecovery and error correction at the mobile station 16. Again, thechannel coding for a particular mobile station 16 is based on the CQI.In some implementations, the channel encoder logic 50 uses known Turboencoding techniques. The encoded data is then processed by rate matchinglogic 52 to compensate for the data expansion associated with encoding.

Bit interleaver logic 54 systematically reorders the bits in the encodeddata to minimize the loss of consecutive data bits. The resultant databits are systematically mapped into corresponding symbols depending onthe chosen baseband modulation by mapping logic 56. Preferably,Quadrature Amplitude Modulation (QAM) or Quadrature Phase Shift Key(QPSK) modulation is used. The degree of modulation is preferably chosenbased on the CQI for the particular mobile station. The symbols may besystematically reordered to further bolster the immunity of thetransmitted signal to periodic data loss caused by frequency selectivefading using symbol interleaver logic 58.

At this point, groups of bits have been mapped into symbols representinglocations in an amplitude and phase constellation. When spatialdiversity is desired, blocks of symbols are then processed by space-timeblock code (STC) encoder logic 60, which modifies the symbols in afashion making the transmitted signals more resistant to interferenceand more readily decoded at a mobile station 16. The STC encoder logic60 will process the incoming symbols and provide “n” outputscorresponding to the number of transmit antennas 28 for the base station14. The control system 20 and/or baseband processor 22 as describedabove with respect to FIG. 5 will provide a mapping control signal tocontrol STC encoding. At this point, assume the symbols for the “n”outputs are representative of the data to be transmitted and capable ofbeing recovered by the mobile station 16.

For the present example, assume the base station 14 has two antennas 28(n=2) and the STC encoder logic 60 provides two output streams ofsymbols. Accordingly, each of the symbol streams output by the STCencoder logic 60 is sent to a corresponding IFFT processor 62,illustrated separately for ease of understanding. Those skilled in theart will recognize that one or more processors may be used to providesuch digital signal processing, alone or in combination with otherprocessing described herein. The IFFT processors 62 will preferablyoperate on the respective symbols to provide an inverse FourierTransform. The output of the IFFT processors 62 provides symbols in thetime domain. The time domain symbols are grouped into frames, which areassociated with a prefix by prefix insertion logic 64. Each of theresultant signals is up-converted in the digital domain to anintermediate frequency and converted to an analog signal via thecorresponding digital up-conversion (DUC) and digital-to-analog (D/A)conversion circuitry 66. The resultant (analog) signals are thensimultaneously modulated at the desired RF frequency, amplified, andtransmitted via the RF circuitry 68 and antennas 28. Notably, pilotsignals known by the intended mobile station 16 are scattered among thesub-carriers. The mobile station 16, which is discussed in detail below,will use the pilot signals for channel estimation.

Reference is now made to FIG. 6 to illustrate reception of thetransmitted signals by a mobile station 16, either directly from basestation 14 or with the assistance of relay 15. Upon arrival of thetransmitted signals at each of the antennas 40 of the mobile station 16,the respective signals are demodulated and amplified by corresponding RFcircuitry 70. For the sake of conciseness and clarity, only one of thetwo receive paths is described and illustrated in detail.Analog-to-digital (A/D) converter and down-conversion circuitry 72digitizes and down converts the analog signal for digital processing.The resultant digitized signal may be used by automatic gain controlcircuitry (AGC) 74 to control the gain of the amplifiers in the RFcircuitry 70 based on the received signal level.

Initially, the digitized signal is provided to synchronization logic 76,which includes coarse synchronization logic 78, which buffers severalOFDM symbols and calculates an auto-correlation between the twosuccessive OFDM symbols. A resultant time index corresponding to themaximum of the correlation result determines a fine synchronizationsearch window, which is used by fine synchronization logic 80 todetermine a precise framing starting position based on the headers. Theoutput of the fine synchronization logic 80 facilitates frameacquisition by frame alignment logic 84. Proper framing alignment isimportant so that subsequent FFT processing provides an accurateconversion from the time domain to the frequency domain. The finesynchronization algorithm is based on the correlation between thereceived pilot signals carried by the headers and a local copy of theknown pilot data. Once frame alignment acquisition occurs, the prefix ofthe OFDM symbol is removed with prefix removal logic 86 and resultantsamples are sent to frequency offset correction logic 88, whichcompensates for the system frequency offset caused by the unmatchedlocal oscillators in the transmitter and the receiver. Preferably, thesynchronization logic 76 includes frequency offset and clock estimationlogic 82, which is based on the headers to help estimate such effects onthe transmitted signal and provide those estimations to the correctionlogic 88 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready forconversion to the frequency domain using FFT processing logic 90. Theresults are frequency domain symbols, which are sent to processing logic92. The processing logic 92 extracts the scattered pilot signal usingscattered pilot extraction logic 94, determines a channel estimate basedon the extracted pilot signal using channel estimation logic 96, andprovides channel responses for all sub-carriers using channelreconstruction logic 98. In order to determine a channel response foreach of the sub-carriers, the pilot signal is essentially multiple pilotsymbols that are scattered among the data symbols throughout the OFDMsub-carriers in a known pattern in both time and frequency. Continuingwith FIG. 6, the processing logic compares the received pilot symbolswith the pilot symbols that are expected in certain sub-carriers atcertain times to determine a channel response for the sub-carriers inwhich pilot symbols were transmitted. The results are interpolated toestimate a channel response for most, if not all, of the remainingsub-carriers for which pilot symbols were not provided. The actual andinterpolated channel responses are used to estimate an overall channelresponse, which includes the channel responses for most, if not all, ofthe sub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information,which are derived from the channel responses for each receive path areprovided to an STC decoder 100, which provides STC decoding on bothreceived paths to recover the transmitted symbols. The channelreconstruction information provides equalization information to the STCdecoder 100 sufficient to remove the effects of the transmission channelwhen processing the respective frequency domain symbols.

The recovered symbols are placed back in order using symbolde-interleaver logic 102, which corresponds to the symbol interleaverlogic 58 of the transmitter. The de interleaved symbols are thendemodulated or de-mapped to a corresponding bit stream using de-mappinglogic 104. The bits are then de-interleaved using bit de-interleaverlogic 106, which corresponds to the bit interleaver logic 54 of thetransmitter architecture. The de-interleaved bits are then processed byrate de-matching logic 108 and presented to channel decoder logic 110 torecover the initially scrambled data and the CRC checksum. Accordingly,CRC logic 112 removes the CRC checksum, checks the scrambled data intraditional fashion, and provides it to the de-scrambling logic 114 forde-scrambling using the known base station de-scrambling code to recoverthe originally transmitted data 116.

In parallel to recovering the data 116, a CQI, or at least informationsufficient to create a CQI at the base station 14, is determined andtransmitted to the base station 14. As noted above, the CQI may be afunction of the carrier-to-interference ratio (CR), as well as thedegree to which the channel response varies across the varioussub-carriers in the OFDM frequency band. For this embodiment, thechannel gain for each sub-carrier in the OFDM frequency band being usedto transmit information is compared relative to one another to determinethe degree to which the channel gain varies across the OFDM frequencyband. Although numerous techniques are available to measure the degreeof variation, one technique is to calculate the standard deviation ofthe channel gain for each sub-carrier throughout the OFDM frequency bandbeing used to transmit data.

In some embodiments, a relay station may operate in a time divisionmanner using only one radio, or alternatively include multiple radios.

FIGS. 1 to 6 provide one specific example of a communication system thatcould be used to implement embodiments of the application. It is to beunderstood that embodiments of the application can be implemented withcommunications systems having architectures that are different than thespecific example, but that operate in a manner consistent with theimplementation of the embodiments as described herein.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

What is claimed is:
 1. A method for uplink signaling between a basestation and an access terminal of a plurality of access terminals, themethod comprising: by the base station: assigning resources for aresource request to the access terminal, the assigned resourcescomprising periodic time-frequency resources of an orthogonal frequencydivision multiplexing (OFDM) based signaling scheme; and receiving theresource request combined with acknowledge (ACK) and/or negativeacknowledge (NACK) feedback from the access terminal, wherein theresource request is spread over a plurality of subcarriers in one ormore OFDM symbols of the assigned resources using at least oneorthogonal spreading sequence.
 2. The method of claim 1, wherein theperiodic time-frequency resources comprise localized or distributedtime-frequency resources in a plurality of OFDM symbols and a pluralityof sub carriers.
 3. The method of claim 1, wherein the resource requestcomprises an indicator or a flag.
 4. The method of claim 3, wherein theresource request comprises a request for uplink resources for the accessterminal.
 5. The method of claim 1, further comprising the base stationidentifying the access terminal from which the resource request istransmitted based at least in part on the resources on which theresource request is received.
 6. The method of claim 1, wherein theresources for the resource request assigned to the access terminalcomprise resources overlaid on time-frequency resources used for uplinkcontrol signaling.
 7. The method of claim 1, wherein the resources forthe resource request assigned to the access terminal comprisetime-frequency resources assigned at least in part to a second accessterminal of the plurality of access terminals, the second accessterminal using at least one orthogonal spreading sequence that differsfrom the at least one orthogonal spreading sequence used by the accessterminal.
 8. A base station configured to receive uplink signaling froman access terminal of a plurality of access terminals, the base stationcomprising: wireless circuitry for performing wireless communicationwith the plurality of access terminals; processing circuitry incommunication with the wireless circuitry, wherein the processingcircuitry is configured to cause the base station to: assign resourcesfor a resource request to the access terminal, the assigned resourcescomprising periodic time-frequency resources of an orthogonal frequencydivision multiplexing (OFDM) based signaling scheme; and receive theresource request combined with acknowledge (ACK) and/or negativeacknowledge (NACK) feedback from the access terminal, wherein theresource request is spread over a plurality of subcarriers in one ormore OFDM symbols of the assigned resources using at least oneorthogonal spreading sequence.
 9. The base station of claim 8, whereinthe periodic time-frequency resources comprise localized or distributedtime-frequency resources in a plurality of OFDM symbols and a pluralityof subcarriers.
 10. The base station of claim 8, wherein the resourcerequest comprises an indicator or a flag.
 11. The base station of claim10, wherein the resource request comprises a request for uplinkresources for the access terminal.
 12. The base station of claim 8,wherein the processing circuitry is further configured to cause the basestation to identify the access terminal from which the resource requestis transmitted based at least in part on the resources on which theresource request is received.
 13. The base station of claim 8, whereinthe resources for the resource request assigned to the access terminalcomprise resources overlaid on time-frequency resources used for uplinkcontrol signaling.
 14. The base station of claim 8, wherein theresources for the resource request assigned to the access terminalcomprise time-frequency resources assigned at least in part to a secondaccess terminal of the plurality of access terminals, the second accessterminal using at least one orthogonal spreading sequence that differsfrom the at least one orthogonal spreading sequence used by the accessterminal.
 15. A non-transitory computer-readable medium storinginstructions that, when executed by processing circuitry of a basestation, case the base station to: assign resources for a resourcerequest to the access terminal, the assigned resources comprisingperiodic time-frequency resources of an orthogonal frequency divisionmultiplexing (OFDM) based signaling scheme; and receive the resourcerequest combined with acknowledge (ACK) and/or negative acknowledge(NACK) feedback from the access terminal, wherein the resource requestis spread over a plurality of subcarriers in one or more OFDM symbols ofthe assigned resources using at least one orthogonal spreading sequence.16. The non-transitory computer-readable medium of claim 15, wherein theperiodic time-frequency resources comprise localized or distributedtime-frequency resources in a plurality of OFDM symbols and a pluralityof subcarriers.
 17. The non-transitory computer-readable medium of claim15, wherein the resource request comprises an indicator or a flag thatindicates a request for uplink resources for the access terminal. 18.The non-transitory computer-readable medium of claim 15, whereinexecution of the instructions by processing circuitry further cause thebase station to identify the access terminal from which the resourcerequest is transmitted based at least in part on the resources on whichthe resource request is received.
 19. The non-transitorycomputer-readable medium of claim 15, wherein the resources for theresource request assigned to the access terminal comprise resourcesoverlaid on time-frequency resources used for uplink control signaling.20. The non-transitory computer-readable medium of claim 15, wherein theresources for the resource request assigned to the access terminalcomprise time-frequency resources assigned at least in part to a secondaccess terminal of the plurality of access terminals, the second accessterminal using at least one orthogonal spreading sequence that differsfrom the at least one orthogonal spreading sequence used by the accessterminal.